So from all the variables in a boxers program and all his training through the years you've narrowed it down to his use of punching with dumbells? How do you know it's not the way he wipes his ass? He has that ass wiping technique and has crushing power, what more do you want?
You're a special kind of stupid.

There is a direct quote from Abraham himself stating the benefits of said practice. Pray tell, were you born a pea-brained berk or did you fall and bang your gormless bonce?